Latching device for injection molds with removable inserts

ABSTRACT

A latching device ( 20 ) for a mold assembly ( 10 ) uses a cam action to hold the “A” side plate against the hot runner system/nozzle plate ( 18 ) during operation. Preferably, a latch ( 20 ) is provided on each side of the mold to effectively hold the “A” side plate against the nozzle plate ( 18 ) during the high pressure injection of plastic melt. For purposes of a mold insert change, each latch ( 20 ) is rotated to release the “A” side plate from the nozzle plate ( 18 ), and hold the “A” side plate against the “B” side plate. This enables the “A” ( 12 ) and “B” ( 14 ) portions of the mold assembly to be moved away from the nozzle plate ( 18 ), thereby avoiding interference of the hot runner nozzles and “A” side insert and enabling quick mold insert change.

This application claims the benefit of provisional application Ser. No.60/212,150 filed Jun. 16, 2000.

TECHNICAL FIELD

The present invention relates to molds used in injection moldingmachines. More particularly, the present invention relates to a latchingdevice for use with an injection mold that includes removable inserts,to facilitate removal or changing of the mold inserts.

BACKGROUND ART

An injection molding machine operates so rapidly that it can quicklyfinish a run of a particular molded part in a comparatively short periodof time. In view of the substantial cost of the machine, it should notbe allowed to sit idle. When changing the set-up of the molding machinefrom production of one part to another, the article-forming mold in themachine has to be removed and a new mold inserted so that the machinecan begin to operate and produce the new molded part. The time taken inchanging the mold must be minimized so the machine can begin productiveuse as soon as possible. It currently takes from one to several hours tocomplete a complete mold change. The time lost in the mold changeprocess has a marked effect on the profitability of a molding business.

Master Unit Die Products, Inc. (“MUD”) significantly reduced the timerequired for mold changes with its invention of a “Quick Change Systemfor Mold Bases” as described in U.S. Pat. No. 5,350,289. The MUD quickchange system is used with molds having adapter frames that are attachedto the platens of the injection molding machine. The adapter frames arereadily transferable from machine to machine using the existing mountinghole patterns on the platens of the machines. The molds are typicallysupported on ear plates that are adapted to support many different sizemolds. The ear plates are also readily transferable from adapter frameto adapter frame. The adapter frames have a U-shaped guide and supportchannel for receiving the ear plates on the mold base. T-shaped guiderollers are mounted in line with the entrance to each side of the guidechannel. The T-shape configuration for the guide rollers enables theedge of the ear plate to roll along the vertical portion of the “T”while the larger horizontal portion of the “T” captures the ear plate,keeping the ear plate in line with the guide channel on the adapterframe. The adapter frames are attached to the platen faces using theexisting standard threaded hole pattern on the platen face. Clamps canbe used for the initial installation of the adapter frame. The clampsare preferably removed after bolts or cap screws, or the like, are usedto fasten the adapter plates to the face of the platen. When the earplate is inserted into the adapter frame, all of the fasteners arecovered, eliminating a potential source of damage during the operationof the machine. The MUD quick change system allows mold assemblies thatare equipped with standard ear plates to be changed in a molding machinein ten minutes, or even less time.

However, when the MUD frame is used with a hot runner manifold system,the “A” side frame that accepts the “A” side insert is bolted to the hotrunner system nozzle plate. If the MUD inserts need to be changed to adifferent set, the “A” side mounting screws have to be removed, and the“A” side has to be pulled away from the hot runner system, so that thenozzles are pulled out of the seal-off and gate well in the mold frame.This is necessary to obtain sufficient clearance so that the nozzles ofthe hot runner system do not interfere with removal of the inserts andinstallation of the replacement mold inserts. The removal of the “A”side mounting screws is time consuming and slows the process of changingthe mold inserts significantly, somewhat negating the advantage of theMUD quick change concept.

DISCLOSURE OF INVENTION

Briefly stated, in accordance with one aspect of the present invention,a latching device is provided that uses a cam action to hold the “A”side plate against the hot runner system (nozzle plate) duringoperation, thus replacing the screws used in prior art moldconstructions. Preferably, the latching device is provided on each sideof the mold to hold most effectively the “A” side plate against thenozzle plate during the high pressure injection of plastic melt.

For purposes of a mold insert change, each latch is rotated to releasethe “A” side plate from the nozzle plate, and hold the “A” side plateagainst the “B” side of the mold. This enables the “A” and “B” portionsof the mold assembly to be moved away from the nozzle plate, therebyavoiding interference between the hot runner nozzles and “A” side insertand enabling quick mold insert change.

The latching device of the present invention includes dowel pins in boththe nozzle plate and “B” side plate. A pivoting latch arm is configuredto engage one or the other of the pins, depending on the function to beperformed. The latch arm pivots on a center hub with and offset toprovide a cam-tightening effect when the hub is rotated by a latchlever. The latch is engaged with the dowel in the nozzle plate duringoperation. To perform a mold insert change: (i) the clamp mechanism ofthe molding machine is operated to close the mold, (ii) the center hubof the latching device is rotated using a lever to release the latchingforce between the “A” side and nozzle plate, (iii) the latch arm isrotated to engage the pin on the “B” side, (iv) the center hub isrotated by the latch lever to generate a latching force between the “A”and “B” sides, (v) a safety pin is inserted in the latch arm, (vi) theclamp mechanism of the molding machine is operated to open the mold,moving the “B” and “A” sides together to clear the hot runner nozzles,(vii) the mold inserts are removed, (viii) new mold inserts areinstalled, and (ix) sequence is reversed so that latch arm ends tightlyengaged with the pin in the nozzle plate.

Accordingly, the latching device of the present invention provides for atime-saving means of releasing and connecting a mold assembly and a hotrunner manifold system.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a side view of an injection mold assembly shown open with thelatching device of the present invention engaged to hold the “A” sideplate to the nozzle plate of a hot runner system.

FIG. 2 is a side view of an injection mold assembly similar to FIG. 1,except that it is shown in a closed position.

FIG. 3 is a side view of an injection mold assembly similar to FIG. 2,showing movement of the latch lever to rotate the center hub of thelatching device of the present invention, thereby releasing the camforce.

FIG. 4 is a side view of an injection mold assembly similar to FIG. 3,showing how the latch arm is rotated to engage the dowel pin in the “B”side plate.

FIG. 5 is a side view of an injection mold assembly similar to FIG. 4,showing movement of the latch lever to rotate the center hub of thelatching device of the present invention, thereby applying a cam forceto hold the “A” and “B” plates together.

FIG. 6 is a side view of an injection mold assembly similar to FIG. 5,showing the mold opened with the latching device of the presentinvention engaged to hold the “A” and “B” side plates together, so thatthe “A” side plate is moved away from the nozzle plate.

FIG. 7 is a side view of an injection mold assembly similar to FIG. 6,showing the mold open and the mold inserts being removed from the top ofthe “A” and “B” mold sections.

FIG. 8 is a side view of the center hub of the latching device of thepresent invention.

FIG. 9 is a top plan view of the center hub of the latching device ofthe present invention.

FIG. 10 is a sectional view of the center hub of the latching device ofthe present invention, taken along the line 10—10 of FIG. 9.

FIG. 11 is a sectional view of the center hub of the latching device ofthe present invention, taken along the line 11—11 of FIG. 9.

FIG. 12 is a top plan view of the latch arm of the latching device ofthe present invention.

FIG. 13 is a sectional view of the latch arm of the latching device ofthe present invention, taken along the line 13—13 of FIG. 12.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring now to the drawings, particularly FIGS. 1 and 2, a moldassembly 10 is shown that incorporates a latching device 20 according tothe present invention. For purposes of illustration, the invention willbe described in connection with the MUD quick change mold system as usedwith mold bases having adapter frames that are attached to the platensof an injection molding machine. The MUD quick change system is suppliedby Master Unit Die Products, Inc. (“MUD”) and is described in detail inU.S. Pat. No. 5,350,289, which is incorporated herein by reference.However, it should be understood that the latching device of the presentinvention can be used in a variety of mold constructions for thepurposes described herein, i.e., releasably holding mold elementstogether while various operations are performed.

Typically, as shown in the drawings, a mold assembly 10 has a cavitymold portion 11 and a core mold portion 13 that are included as part ofa mold insert assembly 15. For purposes of simplifying this description,the cavity mold portion 11 will be referred to as part of the “A” side12 of the mold 10, and the core mold portion 13 as part of the “B” side14. As is understood in the art, each of the “sides” of the mold areformed in a multiple plate construction that varies-depending on thedesign of the molded part and the functions to be performed by themechanisms contained in the mold assembly 10. Plastic melt is conveyedto the “A” side 12 by a hot runner system (not shown) including a nozzleretainer plate 18, as is generally known in the industry. D-M-E Company,the assignee of the present invention supplies a variety of moldconstructions consistent with the purposes of this invention.

The latching device 20 includes a latch arm 22 having opposed hooks40,42 at one end and a pivot hole 44 at the other end; see FIGS. 12 and13. The latch arm 22 mounts on a center hub 24 that is rotatablyattached to the “A” side 12 by means of a shoulder bolt 26. The centerhub 24 is configured so that the centerline of the hole 56 used to mountthe hub 24 to the mold is offset slightly with respect to the axis of acylindrical bearing surface 46 that is received in the hole 44 of thelatch arm 22. This offset facilitates a camming action in the latchingdevice 20, as will be more fully described below. With the constructionshown in the drawings, one latching device 20 would be provided on eachside of the mold assembly 10. Since the latches would essentially be the“mirror image” of each other, only one will be described in detail.

For facilitate operation the latching device 20, a latch lever 28 isattached to the center hub 24, which provides mechanical advantage inrotating the hub 24. For further ease of operation, handles 48, 50 canbe provided on the latch arm 22 and latch lever 28, respectively. Thecenter hub 24 is also provided with stop pins 36, 38 to limit the degreeof rotation. In particular, the stop pins 36, 38 cooperate with a pin 54in latch arm 22 for this purpose.

To retain the latch lever 22 in the desired position, a safety pin 30 isprovided. The safety pin 30 is simply a cylindrical pin that is insertedthrough a hole 52 in the latch arm 22 and into an aligning hole ineither the nozzle retainer plate 18 or “B” side 14 of the mold 10,depending on the position of the latch arm 22. The latching device 20 ofthe present invention includes a dowel pin 32 in both the nozzleretainer plate and a dowel pin 34 in the “B” side 14 of the mold forthis purpose.

The latching device 20 is engaged with the dowel 32 in the nozzle plate18 during operation. For a mold insert change: (i) the mold assembly 10is closed, (ii) the center hub 24 is rotated by the latch lever 28 torelease the latching force between the “A” side 12 and nozzle plate 18,(iii) the latch arm 22 is rotated to engage the 34 pin on the “B” side14, (iv) the center hub 24 is rotated by the latch lever 28 to generatea latching force between the “A” side 12 and “B” side 14, (v) the safetypin 30 is inserted in the latch arm 22, (vi) the mold assembly 10 isopened so that the “A” side 12 (now attached to the “B” side 14) clearthe hot runner nozzles, (vii) the mold inserts are removed, (viii) newmold inserts are installed, and (ix) sequence is reversed so that latcharm 22 ends tightly engaged with the pin 32 in the nozzle plate 18.

The operation of the latching device is shown sequentially in FIG. 1through FIG. 7. FIG. 1 shows the mold assembly 10 as it would be innormal operation: the latch arm 22 engaged with the dowel pin 32 in thenozzle retaining plate 18 plate; the center hub 24 positioned so thatthe stop pin 36 is against the pin 54, applying a camming force by meansof the offset bearing surface 46; the safety pin 30 keeps the latch arm22 in the engaged position; the hot runner nozzles (not shown) areseated in the “A” side 12 of the mold 10. In preparation for changingthe mold inserts, the mold 10 is closed, as shown in FIG. 2. With themold 10 closed, the safety pin 30 is removed, the center hub 24 isrotated by means of the latch lever 28 until the stop pin 38 contactsthe pin 54, to release the latching force provided by the cam in thecenter hub 24, as shown in FIG. 3.

The latch arm 22 can then be rotated as shown in FIG. 4 so that itengages the dowel pin 34 in the “B” side 14 of the mold 10. Furtherrotation of the center hub 24 by means of the latch handle 28 until thestop pin 38 contacts pin 54 will provide the camming action to hold the“A” side against the “B” side, as shown in FIG. 5. The safety pin 30 isinserted to hold the latch arm 22 in position. With the latching device20 in this position, the clamp mechanism is operated to open the mold 10a distance “X” as illustrated in FIG. 6. The nozzles of the hot runnersystem will now clear the “A” side 12 so that the mold inserts thatactually comprise the cavity mold portion 12 and a core mold portion 14can be removed from the top of the mold 10; see FIG. 7.

INDUSTRIAL APPLICABILITY

The foregoing discussion and the illustrated embodiment of the inventionteach a latching device that uses a cam action to hold the “A” sideplate against the hot runner nozzle plate during operation, thusreplacing the screws used in prior art mold constructions. Preferably,the latching device is provided on each side of the mold to hold mosteffectively the “A” side plate against the nozzle plate during the highpressure injection of plastic melt.

Although particular embodiments of the present invention have beenillustrated and described, it will be apparent to those skilled in theart that changes in modifications can be made without departing from theconcepts of the present invention. Accordingly, it is intended toencompass within the appended claims all such changes and modificationsthat fall within the scope of the present invention.

What is claimed is:
 1. A latching device (20) to facilitate removal orinstallation of replaceable cavity and core inserts in an injection moldassembly (10), characterized in that the latching device (20) comprisesa latch arm 22 having opposed hooks 40,42 at one end and a pivot hole 44at the other end, the pivot hole 44 of the latch arm 22 mounting on acenter hub 24 that is rotatably attached to one side (12) of the moldassembly by means of an axial bore (56), the center hub 24 beingconfigured so that the axial bore (56) is offset slightly with respectto the axis of a cylindrical bearing surface (46) that is received inthe pivot hole 44 of the latch arm 22, such that this offset creates acamming action in the latching device 20 when the center hub 24 isrotated relative to the latch arm
 22. 2. A method of changing cavity andcore inserts of a mold assembly in an injection molding machinecomprising the steps of: (a) operating a clamp mechanism of the moldingmachine to close the mold assembly, (b) rotating a center hub of alatching device using a lever to release the latching force between an“A” side of the mold assembly and a nozzle plate in the mold assembly(c) rotating a latch arm to engage a pin on a “B” side of the moldassembly, (d) rotating the center hub to generate a latching forcebetween the “A” and “B” sides of the mold assembly, (e) inserting asafety pin in the latch arm, (f) operating the clamp mechanism of themolding machine to open the mold, moving the “B” and “A” sides togetherto clear hot runner nozzles of the mold assembly, (g) removing thecavity and core from the mold assembly, (h) installing new cavity andcore in the mold assembly, and (i) reversing the procedure of steps(a)-(f) so that the latch arm ends tightly engaged with the pin in thenozzle plate and the mold is ready for production.